WANTED: Source For Micro-Miniature Lamps, 12v 25mA Rating

[EADGBE]

Nakamichi used some VERY small incandescent light bulbs in their tape
decks for various lighting jobs.

I'm having trouble finding an equivalent lamp for my Nakamichi to
light the individual function keys (Stop, Play, Rec, etc.).

Where can I find a micro-miniature light bulb with the following
specifications:

Voltage/Current: 12 volts, 25 mA rating.

Size of Bulb: Approximately 3 mm wide, 6 mm long

Contact Type: Wire leads (for soldering into PC board)

PLEASE...don't tell me that I can use a light bulb with a higher mA
rating and just connect a resistor in series to drop the current load
down...I do NOT have room enough for a resistor behind the function
keys.

The kind of bulb I am looking for is sometimes called a "grain of
wheat" bulb or a "grain of rice" bulb, because of its very small size.

Is anything comparable available out there? Thanks in advance....

[GregS]

In article om>, EADGBE > wrote:
>
>Nakamichi used some VERY small incandescent light bulbs in their tape
>decks for various lighting jobs.
>
>I'm having trouble finding an equivalent lamp for my Nakamichi to
>light the individual function keys (Stop, Play, Rec, etc.).
>
>Where can I find a micro-miniature light bulb with the following
>specifications:
>
>Voltage/Current: 12 volts, 25 mA rating.
>
>Size of Bulb: Approximately 3 mm wide, 6 mm long
>
>Contact Type: Wire leads (for soldering into PC board)
>
>PLEASE...don't tell me that I can use a light bulb with a higher mA
>rating and just connect a resistor in series to drop the current load
>down...I do NOT have room enough for a resistor behind the function
>keys.
>
>The kind of bulb I am looking for is sometimes called a "grain of
>wheat" bulb or a "grain of rice" bulb, because of its very small size.
>
>Is anything comparable available out there? Thanks in advance....
>

Probably Radio Shack. The ones I saw had twisted leads attached to
the lamp.

25 ma. is pretty small, but LEDs could be used with a dropping resistor.

greg

[mick]

On Fri, 27 Apr 2007 11:40:31 -0700, EADGBE wrote:

> Nakamichi used some VERY small incandescent light bulbs in their tape
> decks for various lighting jobs.
>
> I'm having trouble finding an equivalent lamp for my Nakamichi to light
> the individual function keys (Stop, Play, Rec, etc.).
>
> Where can I find a micro-miniature light bulb with the following
> specifications:
>
> Voltage/Current: 12 volts, 25 mA rating.
>
> Size of Bulb: Approximately 3 mm wide, 6 mm long
>
> Contact Type: Wire leads (for soldering into PC board)
>
> PLEASE...don't tell me that I can use a light bulb with a higher mA
> rating and just connect a resistor in series to drop the current load
> down...I do NOT have room enough for a resistor behind the function
> keys.
>
> The kind of bulb I am looking for is sometimes called a "grain of wheat"
> bulb or a "grain of rice" bulb, because of its very small size.
>
> Is anything comparable available out there? Thanks in advance....


Try a model engineering shop. They used to be used a lot on model railway
layouts. I suspect they still are, because LEDs just look wrong!

I think Rapid Electronics still carry them.

Maplin WQ13P may be suitable too.

--
Mick (Working in a M$-free zone!)
Remove blockage to use my email address
Web: http://www.nascom.info & http://mixpix.batcave.net

[Dave Plowman (News)]

In article om>,
EADGBE > wrote:
> Where can I find a micro-miniature light bulb with the following
> specifications:

> Voltage/Current: 12 volts, 25 mA rating.

> Size of Bulb: Approximately 3 mm wide, 6 mm long

> Contact Type: Wire leads (for soldering into PC board)

That sounds exactly like the bulbs used for illuminating the switches in
my car - although the wires are bent up the sides for socket connection.

Have you tried a car accessory shop? I'm pretty sure I've seen them in
Halfords.

--
*Never kick a cow pat on a hot day *

Dave Plowman London SW
To e-mail, change noise into sound.

[Mark D. Zacharias]

EADGBE wrote:
> Nakamichi used some VERY small incandescent light bulbs in their tape
> decks for various lighting jobs.
>
> I'm having trouble finding an equivalent lamp for my Nakamichi to
> light the individual function keys (Stop, Play, Rec, etc.).
>
> Where can I find a micro-miniature light bulb with the following
> specifications:
>
> Voltage/Current: 12 volts, 25 mA rating.
>
> Size of Bulb: Approximately 3 mm wide, 6 mm long
>
> Contact Type: Wire leads (for soldering into PC board)
>
> PLEASE...don't tell me that I can use a light bulb with a higher mA
> rating and just connect a resistor in series to drop the current load
> down...I do NOT have room enough for a resistor behind the function
> keys.
>
> The kind of bulb I am looking for is sometimes called a "grain of
> wheat" bulb or a "grain of rice" bulb, because of its very small size.
>
> Is anything comparable available out there? Thanks in advance....

Model railroad hobby shops have oodles of small lamps of various
descriptions.

Mark Z.

[Mike Coatham]

> EADGBE wrote:
>> Nakamichi used some VERY small incandescent light bulbs in their tape
>> decks for various lighting jobs.
>>
>> I'm having trouble finding an equivalent lamp for my Nakamichi to
>> light the individual function keys (Stop, Play, Rec, etc.).
>>
>> Where can I find a micro-miniature light bulb with the following
>> specifications:
>>
>> Voltage/Current: 12 volts, 25 mA rating.
>>
>> Size of Bulb: Approximately 3 mm wide, 6 mm long
>>
>> Contact Type: Wire leads (for soldering into PC board)
>>
>> PLEASE...don't tell me that I can use a light bulb with a higher mA
>> rating and just connect a resistor in series to drop the current load
>> down...I do NOT have room enough for a resistor behind the function
>> keys.
>>
>> The kind of bulb I am looking for is sometimes called a "grain of
>> wheat" bulb or a "grain of rice" bulb, because of its very small size.
>>
>> Is anything comparable available out there? Thanks in advance....
>
Well if you had tried a Google search on "12v wire ended lamps" you would have come up with a multitude of options.
RS Components have them : P/No. 587-670

as does Farnell Electronics: P/No. 1139294

[EADGBE]

Mike:

Thanks for the search, but neither of those lamps are appropriate.

Both the RS Components and the Farnell lamps have the same 60mA
rating. That's too bright and too hot for the application. I did
need a couple of 12v 60mA lamps, which I was able to get quite easily
in my area.

I need the 25mA rating specified by the Nakamichi service manual so
that the lamp will not get too hot or be too bright. These lamps are
only for illuminating the backs of function keys. The lamp sits in a
VERY tight plastic housing with a small translucent window in front of
it. A 60mA lamp would eventually warp this small space because of the
heat it puts out.

I have managed to find a 12v 30mA lamp at an hobby electric train
supplier that is almost half the size of the original Nakamichi lamps
(only 1.7mm wide; originals were 3mm wide). I'm guessing (hoping,
actually) that this lamp will be small enough and close enough to the
25mA rating to be OK.

[Dave Plowman (News)]

In article . com>,
EADGBE > wrote:
> I need the 25mA rating specified by the Nakamichi service manual so
> that the lamp will not get too hot or be too bright. These lamps are
> only for illuminating the backs of function keys. The lamp sits in a
> VERY tight plastic housing with a small translucent window in front of
> it. A 60mA lamp would eventually warp this small space because of the
> heat it puts out.

Fit a LED? Plenty room given your dimensions.

--
*Snowmen fall from Heaven unassembled*

Dave Plowman London SW
To e-mail, change noise into sound.

[Dave Plowman (News)]

In article >,
Dave Plowman (News) > wrote:
> In article om>,
> EADGBE > wrote:
> > Where can I find a micro-miniature light bulb with the following
> > specifications:

> > Voltage/Current: 12 volts, 25 mA rating.

> > Size of Bulb: Approximately 3 mm wide, 6 mm long

> > Contact Type: Wire leads (for soldering into PC board)

> That sounds exactly like the bulbs used for illuminating the switches in
> my car - although the wires are bent up the sides for socket connection.

> Have you tried a car accessory shop? I'm pretty sure I've seen them in
> Halfords.

Just checked a spare - it's around 100 mA. So if you have no success I'd
go down the LED route.

--
*Despite the cost of living, have you noticed how it remains so popular?*

Dave Plowman London SW
To e-mail, change noise into sound.

[EADGBE]

Dave:

When you say that you "checked" a bulb and found it to be 100 mA, how
were you able to determine the mA rating? I have actually found a few
lamps at a model train shop that are labelled "12v" but have no mA
rating. I was wondering how I could check them to see if they could
be appropriate. I have a digital multi-meter, but I am NO expert at
using it!

As for LEDs, I am perfectly willing to go that route if I have to, as
long as the LED's mA rating would be comparable.

Thanks for your help, Dave...and for everyone's else's kind assistance
as well!

[Dave Plowman (News)]

In article om>,
EADGBE > wrote:
> When you say that you "checked" a bulb and found it to be 100 mA, how
> were you able to determine the mA rating? I have actually found a few
> lamps at a model train shop that are labelled "12v" but have no mA
> rating. I was wondering how I could check them to see if they could
> be appropriate. I have a digital multi-meter, but I am NO expert at
> using it!

No use measuring its resistance and working it out, as the cold resistance
is very much lower than the working one - you need to measure the actual
current in use, which is what I did. The DVM has to go in series with the
power source to measure current.

> As for LEDs, I am perfectly willing to go that route if I have to, as
> long as the LED's mA rating would be comparable.

An LED will use a fraction of the current so heat will no longer be a
problem - about a quarter or less of the current for the same subjective
brightness end on. However it's unlikely you'll get one that will look the
same colour as a tungsten signalling bulb of the type you have which is
rather to the red side of white. White LEDs tend to be blue.
A 'basic' LED also requires a series resistor to set the current. For your
purposes 1000 ohms will be fine from a 12 volt supply. Although a limited
selection can also be found with built in resistors. The other problem may
be is that they require a DC supply - although I'd guess the lamp supply
on your tape deck will be this anyway. But worth checking.

Maplin have a fair range of LEDs and it should be possible to make up
something that will fit - and last near enough for ever.

http://www.maplin.co.uk/family.aspx?menu=78&worldid=-2&doy=28m4

> Thanks for your help, Dave...and for everyone's else's kind assistance
> as well!

--
*If your feet smell and your nose runs, you're built upside down.

Dave Plowman London SW
To e-mail, change noise into sound.